Cases like this have got to be a dime a dozen. As much as registering your work with the Library of Congress helps, it won't until you get to the expensive part where lawyers are involved.
I'd like to see YouTube provide the option of registering your work with THEM. If you're the first person to upload specific material to them, that should count as a tie-breaker in such cases as these. They look at the original asteroid video, they look at the subsequently uploaded video (which will also have slightly poorer video quality after being re-encoded), and then the latter video gets denied if they try what they're trying here.
A watermark embedded by YouTube on encoding would also help make it difficult for people to pull material from their site, and repost it as their own.